Ruamāhanga River at Waihenga Bridge

The Ruamāhanga River at Waihenga Bridge is located near Martinborough and is accessed from Bidwills Cutting Rd at the southern end of the State Highway 53 bridge. It is popular for swimming and trout fishing.

The site is monitored by Greater Wellington Regional Council as a part of the Recreational Water Quality Programme, which informs the public about the suitability of sites for recreational activities (see the 'Can I Swim Here' module).

This site is also monitored by NIWA as part of the National River Water Quality Network (NRWQN), which aims to provide an integrated picture of the nation's water quality (See the 'River Water Quality' module).

The safety of water for swimming is determined by measuring ‘faecal indicator bacteria’ (E. coli) which indicates the likely levels of pathogens in the water. Monitoring is conducted on a weekly basis over the summer months (December to March).

Monitoring for the NRWQN is carried out monthly and involves the assessment of water clarity, nitrogen and phosphorus concentration, dissolved oxygen, pH and the concentration of the bacteria Escherichia coli (E. coli). The Macroinvertebrate Community Index (MCI) classifies the site based on the number of and different types of macroinvertebrates living there and is measured annually.

It is generally safe to swim at this site during dry weather. However the site is known to be affected by faecal contamination from rural and urban run-off following heavy or prolonged rainfall. We therefore advise people not to swim for at least two days after heavy rain.

The Cawthron Institute has worked alongside regional councils to verify the processes and methods used for data collection, laboratory analysis of samples collected and the statistical analysis and interpretation of the results presented.

If all Cawthron ticks are green, then you can trust this data. However, if one or more ticks are orange, then conclusions should be treated with some caution.

All samples were collected using approved field protocols and have been analysed in accredited laboratories. Therefore the data shown here has been collected and analysed following best practice.

State

All samples were collected using approved field protocols and have been analysed in accredited laboratories.

Trend - SAMPLING FREQUENCY

Samples are collected monthly at this site. Proposed national guidelines suggest monthly sampling is required for trend analysis. Therefore, any trends shown here are based on best practice in terms of sampling frequency.

Bacteria

E. coli

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State

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State

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NOF Band

N/A

NOF Band

Trend

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Sample history at this site

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E. coli samples for Ruamāhanga River at Waihenga Bridge

n/100ml

What is this graph showing me?

This graph is displaying E. coli concentrations over the selected time period. You can adjust this period by changing the dropdowns. These records form the basis for the state and trend indicators displayed on the dashboard. This data is raw and has not had any methodology applied to it.

What do the icons mean?

For at least half the time, the estimated risk is <1 in 1000 (0.1% risk). The predicted average infection risk is 1%*.

B

For at least half the time, the estimated risk is <1 in 1000 (0.1% risk). The predicted average infection risk is 2%*.

C

For at least half the time, the estimated risk is <1 in 1000 (0.1% risk). The predicted average infection risk is 3%*.

D

20-30% of the time, the estimated risk is >=50 in 1000 (>5% risk). The predicted average infection risk is >3%*.

E

For more than 30% of the time, the estimated risk is >=50 in 1000 (>5% risk). The predicted average infection risk is >7%*.

* The predicted average infection risk is the overall average infection to swimmers based on a random exposure on a random day,
ignoring any possibility of not swimming during high flows or when a surveillance advisory is in place (assuming that the
E. coli
concentration follows a lognormal distribution). Actual risk will generally be less if a person does not swim during high flows.

Clarity

State

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Trend

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Sample history at this site

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Black Disc samples for Ruamāhanga River at Waihenga Bridge

metres

What is this graph showing me?

This graph is displaying Black Disc readings over the selected time period. You can adjust this period by changing the dropdowns. These records form the basis for the state and trend indicators displayed on the dashboard. This data is raw and has not had any methodology applied to it.

State

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Trend

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Sample history at this site

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Turbidity samples for Ruamāhanga River at Waihenga Bridge

NTU

What is this graph showing me?

This graph is displaying Turbidity levels over the selected time period. You can adjust this period by changing the dropdowns. These records form the basis for the state and trend indicators displayed on the dashboard. This data is raw and has not had any methodology applied to it.

Nitrogen

State

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Trend

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Sample history at this site

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Total Nitrogen samples for Ruamāhanga River at Waihenga Bridge

g/m3

What is this graph showing me?

This graph is displaying Total Nitrogen concentrations over the selected time period. You can adjust this period by changing the dropdowns. These records form the basis for the state and trend indicators displayed on the dashboard. This data is raw and has not had any methodology applied to it.

State

State

Trend

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Sample history at this site

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Total Oxidised Nitrogen samples for Ruamāhanga River at Waihenga Bridge

g/m3

What is this graph showing me?

This graph is displaying Total Oxidised Nitrogen concentrations over the selected time period. You can adjust this period by changing the dropdowns. These records form the basis for the state and trend indicators displayed on the dashboard. This data is raw and has not had any methodology applied to it.

Water quality is not considered suitable for the designated use.Impacts on growth of multiple species, and effects starts approaching acute impact level (i.e. risk of death) for sensitive species at higher concentrations (>20 mg/L).

State

State

Trend

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Sample history at this site

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Ammoniacal Nitrogen samples for Ruamāhanga River at Waihenga Bridge

g/m3

What is this graph showing me?

This graph is displaying Ammoniacal Nitrogen concentrations over the selected time period. You can adjust this period by changing the dropdowns. These records form the basis for the state and trend indicators displayed on the dashboard. This data is raw and has not had any methodology applied to it.

Phosphorus

State

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Trend

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Sample history at this site

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Dissolved Reactive Phosphorus samples for Ruamāhanga River at Waihenga Bridge

g/m3

What is this graph showing me?

This graph is displaying Dissolved Reactive Phosphorus concentrations over the selected time period. You can adjust this period by changing the dropdowns. These records form the basis for the state and trend indicators displayed on the dashboard. This data is raw and has not had any methodology applied to it.

What is this graph showing me?

Some sites have telemetry monitoring systems in place that can provide up to the minute data. At
this site the following live data measurements are available. Click on the data type for more information.

Flow

Last 7 days

Last 30 days

Last 12 months

What is this graph showing me?

The live flow estimate for this site.

Live data has not been checked for accuracy before displaying. To give you an idea about how much water that is, 0.7 cumecs (m3/sec) would fill an Olympic swimming pool in an hour. A flow of 42 cumecs (m3/sec) would fill the same pool in a minute.

Disclaimer

The Environmental Data produced by this page should be used as a guide only. LAWA takes no responsibility for the accuracy of information presented, and accepts no liability for actions taken of others based on this information.